DISTRIBUTION OF FMRF-AMIDE-LIKE IMMUNOREACTIVITY IN THE BRAIN AND PITUITARY OF RANA-ESCULENTA DURING DEVELOPMENT

Developmental aspects of the distribution of FMRFamide (Phe-Met-Arg-Ph e-NH2) immunoreactivity (ir) were investigated by indirect immunofluor escence in the brain, pituitary and terminal nerve of the frog, Rana e sculenta. Soon after hatching, FMRFamide neurons were found in the pro ximal terminal nerve, mediobasal olfactory bulb, caudal dorsolateral p allium, diagonal band of Broca, anterior preoptic area, suprachiasmati c area, thalamus, infundibulum, and developing pituitary. FMRFamide fi bers were present in the olfactory epithelium, terminal nerve, olfacto ry bulbs, dorsal and midventral telencephalon, epiphysis. mediolateral thalamus, pretectal pray, optic tectum, infundibulum, posterior inter peduncular nucleus-tegmentum area, and rostral rhombencephalon. During successive developmental stages, ir neurons were no longer observed i n the dorsal telencephalon and pituitary. In late larval stages, ir ne urons appeared in the medial septal area, and ir fibers in the cerebel lum and torus semicircularis. At tile same time, the frequency of ir n eurons increased progressively in the anterior preoptic area. suprachi asmatic area and infundibulum, FMRFamide-ir neurons were never reveale d in mesencephalon and rhombencephalon. Numerous ir fibers terminated in the median eminence and intermediate lobe of the pituitary. The adu lt pattern of distribution of FMRFamide-ir elements in the brain was a chieved during the postmetamorphic development. In light of the existi ng literature, the possible placodal origin of forebrain-located FMRFa mide neurons is briefly discussed.